Mounting



Feb. 2, 1954 N. E. LEE 2,568,033

I MOUNTING File diJuly 7, 1945 asu 1 H 33L 37 23 FIG. 2. an 2||INVENTOR. 23 an. v NORMAN E. LEE

FIG. 4. BY

Patented Feb. 2, 1954 UNITED? MOUNTING Norman'E Iieg Forest Hills, N. Y.

ApplicationiJuly- 7, 1945, Serial N0. 603,-733-: ICIiiLiin?" (Cl.248==358) (Grantediunden Title 35, U. S. Code (1952),

secs

zit; Some areequipped with snubbers whih' com'e* III-1361 -play abruptlywhen the -deflectio'ns re'ach' a certain amplitude and; as a--result,tlieyset-up violent counterforees andregularly recurren't sshockswhichareoften more destructive to "sen sitiVe apparatus than thevibrations and shockswhich the mounts are intended to absorb Again,somemounts are so designed=- that, i if th springmaterial (such asrubber) is injiiredr of vibrations, shocks and noises from said loadilti astoy tearing;or there is aseparationof'a-bond to said base, andvice Versa'.

Some installations requiremounts which will protect against a number ofdillerent-'kindsof;-* impulses. For instance; in aircraft sensitive-ap-- paratus must be shielded from forcedvibrationsof the engines andassociated-parts, at -various speeds; including that speed-at whichthereare generated: vibrations of th'e resonant frequency' of themountedequipment, and also from shocks occurring in rough-air andwvhenlandingiInmarine installations,"provision must be made--- not only againstvibrations "set up' by the enginesw shaftsand propellers-Which operate"at variabl-== speeds, usually of lower frequenciesthan-*in' aincraft;but also against deflections" caused by pitching and rolling of thevessel.

In vehicular installations 'the problem-ismore--' complicated as thesupports mustprovide' pro--- tectionagainst forced vibrations of theengines between the spring material and th -metalpthe mounted -equipment1 may-:separate entirely 'from thebase= and be severe'lydamageds somesupports; havinghydraulic-systems com lfi filprising cylinder and apiston operating therein? have excellent vibration dampingcharacteristics but-arerelatively=large--in size anda'reexpensiveto'-man'ufacture and maintain, and they also-are subject iv to leakage of--the hydraulic medium ZOE-therefrom. In additiongthey are generallygoodin only 'one direction and =they=require aspring system -separatefroin-'the hydraulic system? In 'somemounts; oscillations persist-and add tolater oscill-at'ions' so- *asto' amplify rather than Itis intended bythe-present *inventionto provrdeL-shobk and'vib'ration supports whichare not" attended-'bydefects of earlier mount-s.

It is-an objectof thepresentihVentibnto-pro= and vassociated parts;operating'at'variable' 'speeds;- 30- f vid'e" means of- -supporting'equipment-- whm 111 includin v the natural vibrating'fre'quenciesyvibrations due to substantially uniform; minor 'ir regularities of theroad beds traversedfby the vehicles, which usually have abrupt waveforms;--- and shocks due to holes and abnormalirregularities in the roadsurfaces. These 'conditionsare" greatly exaggerated in thecase' ofmilitary :vehi cles which often mustzcover'terrain-farTougher than thatcovered by other vehicles and"'which" may also be subjected toballisticimpactsand concussions.

Vibration and "shock mounts of the priorart? although used in tremendousquantities;--"have-'* been found to be badly defective in performing"their intended purposes."

Some -mounts are capable of-curtaili-ng tlfe" transfer of vibrationsofrelatively="high 'frequency, but are unsatisfactorybecause'thewallowvibrations at the resonantbrnaturalfrsatisfactorilyisolate and absorb vibrations and shocksofvarious frequenciesr It is'a1so -an object to providea mountwhi'ch may -be stiff enough so as not'to unduly amplify asalow frequency' and resonant frequency oscillationsybut stilt-soft enough to attenuate high fre' quency' oscillationsand thrusts of great" force; without giving'rise to countershocks;

It is another-objectto"providea mount which? -mainorporates'both-ashock' absorbingsystemmnd" aspring systern'in a single unit? It Iis still i another "object "to provide "supports wherein the action ofthe springisystem mam: tates-theoperation of the absorbing system.

It is a still 'f-urth'erobjectto provide su'cli mounts wherein naturalrubber or a'similarm'a; ter-ial ma'ybe" used as the -spring system andvvherein deformations of #said" mate1iai' 'are' utilized ato accelerate-the functioning of the-shock quency of thesupported load "to be-so-greatly' a I amplified as to be seriously detrimental. I

Some: operate to attenuate deflectionsin only one direction .ofmovement; such as :verticalg'an are'ttherefore unsuitedto: installations:requiring attenuation in severaladirectionsr- Iti isxiafurth'enobjieci'fi to provide-"supportin'g='- meansawhichmwillacushiorisdisplacements in- 'di 1 ferent directions;'suchaswertical, horizontal and rotationa1;-

Anotherr object is to employhydraulic 3 d mper;-

ing in mounting devices which are so designed that they will not sufferfrom leakage of the hydraulic medium, which will be small in sizerelative to earlier hydraulic mounts, which will not incorporate solid,nonresilient parts moving against each other with resultant wear, andchanges in operating characteristics and replacement of parts.

It is still another object to proivde mounts in which the hydraulicmedium is confined in ex tensible chambers which provided the necessaryvolumetric capacity for the medium under different conditions ofoperation.

Still another object is to provide mounts having external dimensionswhich allow them to be substituted for presently manufactured mountswithout necessitating structural changes in either the base or the load.7

A still further object is to provide mounts designed to absorb andattenuate shocks in most directions to such a degree as to eliminate theneed of snubbers and thereby avoid the violent countershocks frequentlycaused thereby.

It is still another object to provide mounts wherein metal to metalcontacts are eliminated and hence the transfer of sound, as well asvibration and shock, is inhibited.

It is also an object to provide a mount which, despite unusualvibrations and shocks, and wear and tear, will not allow the equipmentsustained thereby to tear loose entirely from the base.

Generally, a mounting embodying the present invetnion includes a springelement, of a resilient, flexible material (such as natural or synthetic rubber). Said spring element includes an active or effectiveportion (which in some embodiments may be the entire spring element)which I have chosen to call the buckling column portion. When such abuckling column portion is subjected to loading (as in the form of ashock) in an axial direction, it is initially relatively stiff and getssofter (per unit of deflection) and finally gets stiff again at extremeamplitudes. Such a buckling column portion is preferably tubular inshape, and is first put into compression and acts as a column, and then,at a predetermined critical point, collapses and goes into fiexure. Sucha buckling column portion is relatively stiff under normal loads andwill thus prevent undue amplification of the lower frequency vibrations(which are involved particularly in vehicular suspensions), but undersharp surges suddenly gets softer (per unit of deflection), so as toprevent the transmission of large force impulses to the equipment, andthen gets progressively stiffer, so as to stop deflections within theamplitude limitations of the mounting without the need of abruptlyacting snubbers. In the interior of mounts embodying the presentinvention are two hydraulic chambers connected by restricted orificeswhich chambers contain a suitable hydraulic medium. In the use of themount, the hydraulic medium is forced back and forth through saidorifices by deformations of spring elements such as described above.

In order to better understand the structure and function of a bucklingcolumn portion of a spring element, it should be noted that someportions of a spring element may be included only for the purpose ofmechanical coupling and arrangement of the several components of a shockmount, but in every spring element of the buckling type, there is acertain portion which, when subjected to axial thrust, acts as pointed 4out above, that is, it operates in compression as a column under thrustsof lesser degree but it is, nevertheless, free to buckle or collapseinto flexure under thrusts of a greater degree.

A spring element is preferably secured or coupled to the othercomponents of a shock mount so that its operation is controlled so thatit follows a desired mode of operation. The securing or coupling meansmay take various forms. For instance, one or both ends of a springelement may be bonded to a metal member (as by a rubber-to-metal bond orby a suitable adhesive) as are both ends of the spring elements, shownin the drawing, or it may be secured by suitable clamps (not shown).

Sometimes, however, the ends of a spring element are not actuallymechanically secured but they are suitably shaped so that a desired modeof buckling operation occurs. This may be accomplished by having an endof a spring element terminate in a substantially flat and relativelywide surface so that, in operation, it abuts against some other flatsurface and does not rotate. Such a surface keeps a spring element inintimate abutment with a flat plate during the buckling phase of theoperation of the element.

It is highly significant that this accomplishes a triple mode fiexure ofthe spring element (see 3 IU in Fig. 4), that is, flexure occurs atthree different places, via, at the central portion and also at bothends. This causes a tremendous deformation of the material of the rubberof the spring element which is important for at least three reasons; (1)considerable shock energy is dissipated in the work of deforming therubber, (2) this occurs over a longer period of time than the time ofthe shock itself, thereby resulting in isolating a load completely fromthe shock or at least subjecting a load to a considerably lower and lessdamaging acceleration than the acceleration of the shock itself, and (3)considerable restoring force is stored up in the triply flexed rubber,which force is needed to bring the spring element back to its unloadedstate.

Where no portions of a spring element are used for mechanical couplingof the spring element to other components of a shock mount, thenusually, all or substantially all of the axial length of the springelement is free to operate in compression-flexure, as already described,and hence its buckling column portion extends through the entire springelement. However, where the ends of the spring element are secured bymetal clamps or are otherwise constrained as by being widened outconsiderably so that they are not free to undergo compression at onestage of operation, and to undergo buckling at another stage ofoperation, such end portions are not considered to be included in thebuckling column portion. An example of the latter may be seen, forinstance, in my co-pending application Serial Number 603,735, nowmatured as U. S. Patent No. 2,582,998, issued January 22, 1952, wherethe ends of the spring elements are widened out laterally and are alsostiffened by the embedded washers. There the buckling column portion isessentially the vertically disposed web intermediate the widened outends.

.It is to be noted that the ratio of the length of the buckling columnportion, in an axial direction, to its width must be such that, underaxial thrusts of less force than a predetermined critical amount, saidbuckling column portion :thrust-meaehestthisicritiearlamountrtheebuckling acolumnuportionzsuddenly bHGOmGSEHIIStableiaITditbucklesxorwollapses and: goes .intof -ifiexnre. :iIt -sliculd lhe:pointed cont l-thatmhenranfimemberirof 'l-rubberelike material'isiieformed the deformation ufdoes; not-iusually consist. purelyofcompression iorzflexure or-shear. .flRather itii'ssa combination ,ofatwoior :mo're 'of these. :3. Hence, whenwitaiis stated uin': thepresent application uthat ithe f buckling- .ejo1umn 1portion'operatesi1in'-frmo'mpression or in flexure, applicantzintends to-conveyithe fithoughtfithat that isthe :primary or main 51110118 50foperation. ExperieIice 2 has :"in'd-i---cated'zthatiin.'orderitoachievelthe unique buckling type' of:operationireferred -to- 'hereinzathe llength :-;th'e1 bas ':.p1a,t isibeinggubjected t v tmore 191;-

nf-Width iratiocof the =.i.buckling :cclumn po'rti'on nf a-spring fel'ement must be z at least two' -tofione. 'Ifi-it -is lessgthe springzelement will probably remain stable and willaoperiatezrmainly:in''compres- -sion 1irrespective nf-Ethe amount: of i thrust :ap-: plied.@It the sratioiis=at-l=east two to oneg and the bu'ckling :columnlporti'on is otherwiseeu-itably designed, it will act in compressionu'ntil the critical amountof i loadinglis applied, -whereupon it willsuddenly'collapse and itsoperation? *Will then bemainly fiexure. This:-wil1 permit conside'rablymore deflection perunit oi loadthan -w-hen'it-was opera-tingmainly in- -compre'ssion.

preferred 1 embodiment, as illustrated in -*the drawings (Figures l -6Xand-:as hereinafter described "in more detail, comprises a- I load spoolincluding two parallel load -platesjoined by za core; a baseplatehaving-a "central openingter- -min'ating in a tire-like springcollar 1 encircling said core; t'wo generally tubular spring elements,having the op crating characteristics described above, interposed 1respectively "between the =base plate-and each of the load-plates-,--whereby-there *is formedrespectively above :and below--thebase plate two hydraulic-chambers containing a'-suit-=ablehydraulic medium. Said -chambers inter- 'connect byway of restrictedorifices 'such 'as orifices through the base plate and/or the spring"collar; and in-a particular embodiment-ofthein- 'vention, theorifiees-may reside mer'ely ina. labyrinth ofpores 'in athrottling*'-spring 1 collar which is then madeup ofa=permeable=material.

Another preferredembodiment (Figure?) com-- prises= a load-plate and abase "plate spanned by a pair of i concentric spring elements, having'the *operatingcharacteristics described above, -so' arranged that whenthey collapsethe inner-onewfll collapse inwardlyand theouter-oneoutwardly, *wherebytwo hydraulic chambers are formed re-'stricted orifice interconnecting said hydrauliccham-bers and a suitablehydraulic medium-with- -in*the sa-id-chambers. v

*Inthe accompanying drawings "('wherein" for "clarity the hydraulicmedium is notshown) Eigure-l is-a-plan-view of apreferred-formofmounting embodying the present invention, shown initsncrnietl; at rest condition, a portion of the upper load platebrokenaway to show the 'interi'or ofthe mount;

Figure 2 is an-elevationalview, partly sectioned "along-the line' iZ--2; of the moun'tingof Figurel Figure 3 is an enlarged,=fragmentarygperspectti've view: of thebase plate and spring' collarfofthe mount of Figures 1:anda2,1;theiportioniofithe asurfaceii-tolwhich'the upperuspringi element is I :boncled eingdndicated byi brokenilines;

rrEigur r i ea vertical'=.=composite sec'tion taken "along thrfiline i"z of -Eigure 1, whereinr to the left; the parts are shown inith'eireondition when treme lateral deflection to:the rightan'd the spring"fingersare in collapse and=are being subje'cted 'atofflex-urerandFigure' 'l i a verticaicross section of a-modifie'diform of" the presentinvention, wherein a single load plate is used and I the tWo hydraulicehambers are disposed one within "the other.

#Referringmow particularly to Figures 1-6, the (form ofamounting thereshown includes a horizontally disposed base plate I I which is i squarein outsideiconfiguration and is pierced by four =corner-holes l2receivable to bolts-or other -fas- Jtening"mean 'inot showm. Saidbase-plate H is provided with a central circular opening 4'3 andiispierced by several small fixed orifices 1 l5 -arranged inia circleconcentricwith said central opening l3.

ifiixtending concentrically through the opening 13 is1a ve'rticallydisposed,tubular, met'al' core I .35 of Ja load: spool 19. If Secured tothe ends 'of 'said :"core l l are horizo all-y: disposedgupper an'dlower load plateszi U, 2 LL. Said =load 'plates 2 I U 2 IL :may -bejoined tosaid= core 5 I 1 by--wlding-"or any other suitable-means. M0-Encireling the ccre l1, and coaxial therewith, is a spring collar 23-(seeitiartioularly Figure- 3) =-which is :made ofa 1 flexible resilientmaterial asuch a s natural orsynthetic rubb'eiyand which is shapedsubstantially like avhiculartire. Said spring collar 23 is providedwith;a horizontalslot aboutits outer periphery,- in which slot ispos'iti'one"d the inner marginal edge portion 4 of the 'base plate l l lsaid base plate is preferably permanently bonded in saidslot- 2 5. Theupper "and -lower rims 2-lU, ii-1L er the' spring collar encircle theeore 1 l and make a snug sliding fit there- "about.

"-The upper and lower -walls MU, 281, of --'said "spring collar' '23 Iare provided with several narrow, radially disposed slots2tU;-2'9L,which-form "-variable orifices as will be hereinafterexplained, so-* as "to form a plurality of radially? positioned upper'and'lowerspring fingers: 301T, 30L. Said --spring-fingerg "3 U,.. 3liL: .are positioned :substan- 6O tially horizontally and haverelatively flat upper andlower surfaces.

Positioned above thebase plate is aniupper spring'e-lement '3iU of; aresilient fiexiblem'aterial, 'suchasna'turalor jsyntheticirubb'er. Said'spring '55 element-*3 IU is i of such "geometric configuration "that,upon being pressed together longitudinally 'betweenthe base, plate I land the upper "load column under compression and then, with in-"crease'd pressure; will suddenly collapse so as to fiex= i-r1war'dlyand-will be much softer. i

' As sl-"lown in the drawings ,ithe said sprin g memberi31U ma'yLbebounded inwardly andoutwardly by substantially:icylindricalmsuriaces,iexcept the' base plate is in a'sliglitly' upwardly "deflected ithatizthezmutenzbylindricalzisurfacentiszaconeave *aecaoss throughout itscentral portion. The lower end of said upper spring element 3IU issecured, as by a metal to rubber bond, to the upper surface of the baseplate H, outside the circle of orifices l5, in the position indicated bybroken lines in Figure 3. Its upper end is secured to the lower surfaceof an upper circular metal washer 3313, the upper surface of whichwasher 33U is joined to the lower surface of the upper load plate 2 IU,as by seam-welding or in any other suitable manner to make a sealagainst leakage of the hydraulic medium hereinafter referred to.

A similar lower spring member 31L is likewise secured to the base plateH and a similar lower metal washer 33L, which washer 33L is similarlyjoined to the lower load plate 21L.

It will thus be seen that the structure described incorporates threeintercommunicating chambers, the upper and lower hydraulic chambers 35U,35L and the intermediate hydraulic chamber 31, each of which chamber35U, 35L, 31 is generally annular in shape. The upper and lower chambers35U, 35L communicate with each other through the fixed orifices l andalso, by way of the intermediate chamber 31, through the upper and lowervariable, slot-type orifices 29U, 29L. Said chambers 35U, 35L, 31 arefilled with a suitable hydraulic medium (which, for clarity, is notindicated in the drawings). Said hydraulic medium may be a liquid, suchas a viscous oil or the like, or a gas, such as air, or a combination ofliquid and gas.

In describing the operation of the mounting aforesaid (Figures 1-6), itwill be assumed that it is being used to mount a radio set (not shown)in a motor vehicle (not shown). The base plate H would then be securedto the chassis of the vehicle, by means of bolts (not shown) through theholes l2, and the radio set would be secured to the load spool I9, bymeans of a bolt (not shown) through the hole in the core 11.

As the motor vehicle is operated, the base plate H is subjected tovertical oscillations, resulting in vertical movements of the base plateH. As the base plate II is translated slightly vertically under thrustsof relatively small force, the spring elements 3|U, 31L are subjectedalternately to compression and tension, one of said elements undergoingcompression while the other is undergoing tension (as shown in the lefthalf of Figure 4). However, when the base plate I I is translatedvertically a greater distance due to increased thrusts, the springelements 3IU, 3IL collapse alternately into inward fiexure (asillustrated in the right half of Figure 4).

During vertical translatory movements of the base plate H, as alreadydescribed, the hydraulic medium is caused to flow back and forth betweenchambers 35U, 35L through the fixed orifices i5 and variable orifices29U, 29L.

As shown in the right half of Figure 4, when the base plate l l isdeflected upwardly approaching its extreme upward position, the upperwall 28U of the spring collar 23 is squeezed upwardly against the upperload plate 2IU so as to stop any flow of hydraulic medium through thevariable orifices 29U. Hence, any flow of said medium between thechambers 35U, 35L must then 7 be through the fixed orifices l5. Also,during such relatively large vertical deflections, the upper or lowerhalves of the spring collar 23 are subjected alternately to somedeformation due to being squeezed between the base plate I l and one ofthe load plates 2IU or L.

Horizontal translations of the base plate H he medium between thechambers (Figures 5 and 6), will cause the upper and lower springelements 3IU, 3IL to be subjected to a shearing action. If such lateraldeflections of the base plate II are of relatively small amplitude(Figure 5), the spring fingers 30U, 30L, to one side of the core 11,will act as columns under compressive strain. However, when such lateraldeflections are of greater amplitude (Figure 6), the said spring fingers30U, 30L will collapse upwardly and downwardly, respectively, so as togo into flexure.

It will be noted that, during such lateral deflections, the shapes ofthe hydraulic chambers 35U, 35L are being changed constantly, thusrequiring that the hydraulic medium contained therein be pushed aroundwithin said chambers (even though there may be no how to and fro betweenthe chambers), thereby resulting in an absorption of considerableenergy.

Should there be any twisting or rocking movements imparted to the baseplate H, the mount described has sufficient rotational compliance toattenuate them.

During such rotational movements there will also be an energy absorptiondue to the hydraulic system as there may be some flow of the hydrau-35U, 35L and, in any event, the medium will be pushed around within eachof said chambers in view of the fact that they will be changing shapeconstantly.

Any other movements imparted to the base plate l3 will merely be acombination of the movements already described.

It will be understood that, although the amplitude of the mount justdescribed is limited toward the ends or" vertical strokes, the mountgets progressively stiffer as it approaches a maximum deflection. Thesteady energy absorption by the hydraulic system, combined with theincreasing recovery force stored up in the spring system, as theamplitude of deflection increases, results in a time lag in thedeflection, thereby keeping the amplitude of deflection within thepredetermined limits of a particular mount. Thus, by a steadilyincreasing storage and absorption of energy, the vibrations and shocksare attenuated without the use of bumpers, which may act with aninjurious abruptness.

An important feature of the present invention is that axial deflections,which are large enough to cause collapse of one of the spring elements3111], ML, are, nevertheless, relatively small as compared to thechanges in the relative volumetric capacities of the upper and lowerchambers 35U, 35L. This is accomplished by the fact that deformations ofthe resilient material of the spring elements IHU, ML and the springcollar 23 accelerate a decrease of the volumetric capacity of one of thechambers 35U, 351.. while accelerating an increase of the volumetriccapacity of the other. This acceleration of change in relativevolumetric capacities is particularly advantageous where a hydraulicmedium of low viscosity is used, as it results in a more rapid flow ofthe medium through the restricted orifices and, hence, a greaterabsorption of energy. Low viscosity liquids may sometimes be preferredbecause they may perform more satisfactorily over greater temperatureranges.

It is to be noted also that vertical deflections of considerableamplitude tend to reduce the total volumetric capacity of the threehydraulic chambers 35U, 35L, 3?. If an incompressible hydraulic mediumis being used, the said total volumetric capacity is maintained bysuitable deformation audi-.= stnetchinggofc the (tubular? springmembers. 3,4:I I -31l-L. Theiadditional ienergy requireditoiace)complish such deformatiorraand stretching Willa-be: an: additionaidrainaons thereforcea'causing such extreme deflectionaandewill,therefcme, further assists-m..-increasing;=;,theedamping efiect: of;:the; mount at extremeedeflectionstz Arpreferredlhydraulic medium fortherembodi-l ment)describedrabovee (Eignnesy176) is? a suitable: fluidsuch as oil Howevergitmay sometimes-be advisable -to-use a hydraulic;fluid combined: with acsmalL-amount;ofisaircor other: gas. In someinstallations;this--would :zbe helpful duringa-extremedefieetionswwherev thea'combined: volumetric. capacityofithachambers35H; 35L, 31: might. tend to decrease.lA,compressiblagasawilbthenrelieve excessive.- pressu-resr:andeundue;deformation of: the. spring ielementsdi LU, v3 A compressible:

gasyrwould -w also help toicompensateafon pressurechangeswduewtoatemperaturevariations? 'llheisizes-vand numbers of-thefixed:- orifices 5 andrt-hervariable 'or-i-fices'ZSU; 2 9L: will;ofacourse; bevdeterminedibyg variousifactors; includingethetviscosity-1andtype of; 1 hydraulic 1 :mediumebeing: usedthea-loadiratings; of: the mounts,- etc; b

Assalreadyqindicated; itherloadedefiect-ion char acteristics: :ofthen-embodiment: described :herein'. may be modifiedgsofas toifol1ow-optimumivalues" bychangingytha hydraulic :"actioni during deflectiombyevarying thev-orificesrthroughwhich the; hydraulic medium r must: 1flowbetween i the two chambers wtli 3511.: 'Iwo possible' means for;doing. this; are :shownrherein: .b'lItUitL-Vill be; under? stood,athattsothen:meanslrroti varying;itherorificesmay-'rbemsedi The:tubularnspringnlements 61H; may :besecured directly:to:thewloadxplateswzl U; 21L; if a suitabie'emanufacturingztechnique-"for; accom:-- plishing this is worked out.embodimentdescribied above'; manufacturing procedures di'ctated'vthatsaid spring elements -3 III, 3l1iibeaseeured to;.the: washers-33 U;:33L1which, insturnyare securedrrespectivelyto'theload plates: 21517,; 2iii.

Although a; particular :m'ount will. obviously be designedewithreertainloads iand."vibrations and: shocks in imindy:itriis'rconceivable that;in' use,a

mounti maybesubjectewto unanticipated conchtion'svor: "it'lmay be usedbeyond "the" intended useful life span of its resilientmaterial. thisoccun the -:resilient1'mate'rial may rupture" or the bonds 'between oneof the: spring elements 31 13? S'I I t and'Ithe Washers" 33171331? orthebase plate l I may let go; Nevertheless, the load-will noifisepara'tefrom the base 'and fly into space as the-base plate- H is imprisonedupon the load spool I91 Onepossible imod-ification (not shown in thedrawingso ofthe present invention is the same as the embodiment alreadydescribed (Figures l fil," except that the fixed orifices l5 -and thevariable-:orifices 29Uj 291- are not present at all and a throttlingspring collar is substituted for the-spring collar Saidthrottlingspringcollar may have substantially the same configurationas said springcollar 23, anddiffers'therefrom'only in' thav it is made 'up of I apermeable resilient material',- which s-pierced-by a labyrinth of-extiemely' fine circuitous 'poresi such as felt or possibly a very finesponge rubber. The said pores: take-the placeofthe variable orifices251], 2 915 of the first embodiment: embodiment; the -chambers --3 5U;35L intercommunibate-only througlrthetiny pores-inthe said throttling'spring-bollarfi However, in: the:

Should:

In this modified III 7 Such a modified mount, shaving.- the-permeablethrottling collate as just described, is designed particular-lyior use:with; a lowviscosity liquid or a gaseous. hydraulicrmedium, Forcing sucha me'-- dium through-the :permeable,-rmaterial= of thethrottlingacollarcauses a tunbulenceso that con siderableT-energyista'therebydissipated; In this modified-embodiment, L-the' operation issimilar to the firstwembodiment (Figures 1-6), except thattherihydraulic medium must pass through the ponesot the-throttlingcollan in passing between theechambers;3z5U;. 35L.

When: extremevertical deflections:ofvthabaseplate l-loccun thepassage oithehydraulio mediumlthroug-hzthesa-id-throttlingecolla-nrisz notstopped: entirely,but it is considerably; curtailedas thethrottlingcollar ismrthen squeeaed.-against=oneof the load plates Z-YLU;Zlh-c Thus, itiiss seenlthat -toward the-end ofza: vertical-w stroke;there :is an" increasein the dampingeeffect analogous :to:theincreasealready described-2 in s connection .withithe -first' embodi=ment: 1' r Refierr ingenow mora particularly. 'to- Figure-:7;theamodiflede form? on mounting there "illustrated includeseav flat:metal =ba'se plate 5 I anda "fiat metal: loa'd p1ate.:43,- bothsofWhichare horizon-- tally disposed, the. loadrplatetd3- being: :spacedfromi andfi above the: base plate dl The base plate" 4 l;- may: have":any-convenient peripheral configuration andi'is -here shown ase'square:It is piercedsatrits corners byvseveral fastening holes (not showniz-Therupper'surfacei of? the centra'l portion ofithe baseplatez lliseprovided with one or more, radially disposedy:short;shallowchanmiss-'65:

The loadzrplate '43 iscoficirculan configuration.Extending:axiallyupwardly-from tlre-midpoint of saidloadwplatecdspandrigidlylsecured thereto; as by 'weldingror otherwise;is an internally'threaded bushi'ngd l; :whichds receivQrble twa-fastening bolt (notrshown'h A pairsoficoncentric "spring'e1ementss49; 5l-, are interposedf between the: platesr-A I; .43 2: In' gee--metriczconfiguration; 2said:"springfelements 19-, 5 l are similar rto:therrispring :elementS-"S'I'U, 31D deseribedf abovaz (Figures: 1-6 sothat, under longitiidihalithrustsn of. sufii'i'zientforce; the innerspringcelementtz l'fi collapses 't'inwardly; and the outenspring?element 51: collapses-outwardly. The lowerrtendsilmgrfirofvsaiditubularmembers '49, F5 l are secured bynany :suitable: means suchas by a' metal-.to-rubber bondpdirectl'y tothe'base plate- 4']:Thei'l'oweriendzdfi ofthe'sinner spring element eazispanso the: radial.channels: 45'" and the lowerouter: mis of?said-fchannels dhrA'fpair'of'con-- centrically disposed;: flat; metal: washers 51; 59-

are seeuredx'respectivelyrtothe-upper ends" of the tubularrelements rm-:51: as 'by a" suitable metal-torubloerfsbond"; Saida Washers: 51;59"are in" turn seeurelyifastened ltonthe undersurface of the loadplatewdd, as by seam-welding orother suitable meansza' As-willfbe'seenixthe arrangement of parts 'just" central: hydraulic chamber 6 Ii(which-iinpositionediwithin therinner tubular spring element 49) and aring-shaped chamber Fre iwhich' iencircleszsaidc innerrspringzelement'49 and isL positionednwithin:itheie outer springelem'ent': 513 a.Saidzbhambers 61.3163 .ma'yabe filled with a-ny.suitabierrcompressibleirfluidimedium :(not showni i lwhicha'may v.be:argasy: SUICIIEITaSf air; on a aszwand-z: a liquid; such* as:- aircombination; of an'd glycerme;iheaparticulazrmediunrandvisco 1 itythereoflbeing determinedrb'yltha intendedzus sjoinedzztotithebasei-platezel beyond the:

11 of the mounting. Said chambers 6|, 6'3 intercommunicate through thechannels 45.

In the operation of the mount just described, the base plate 4| may besecured, by suitable fastening means (not shown) such as bolts, to abase (not shown), and a load (not shown) which is to be vibrationallyinsulated from said base, may be secured to the load plate 43 by meansof a bolt (not shown) screwed into the bushing 41. Assuming theinstallation to be of a radio set in a motor vehicle, the vehicle is thebase and the radio set is the load. At rest, the mounting is then in thecondition shown in Figure 7.

During operation of the motor vehicle, the base plate 4| is caused tooscillate. Slight upward deflections cause the spring elements 49, toact as columns under compression and greater upward deflections causethem to collapse into flexture, as already describedin connection withthe first described embodiment (Figures 1-6). During slight upwarddeflections of the base plate 4| the hydraulic medium is compressedslightly. During greater upward deflections, however, due to the inwardand outward flexures of the spring elements 49, 5|, respectively, thechange in the relative volumetric capacities of the hydraulic chambersBI, 63 is so great that a flow of the hydraulic medium through thechannels 45 takes place. As the base plate 4| returns to its normal atrest position, the said medium flows in the opposite direction. Anydownward deflections of the base plate 4| from its normal, at restposition causes tension of the spring elements 49, 5| and expansion ofthe hydraulic medium.

As in the other embodiments of the present invention, axial deflectionsof relatively small amplitude (which are still suflicient however tocause collapse of the spring elements 49, 5|) will cause a relativelylarge change in the relative volumetric capacities of the two hydraulicchambers SI, 63, due to the fact that deformations of the resilientmaterial of the spring elements 49, 5| accelerate an increase of thevolumetric capacity of one of said chambers SI, 63 while accelerating adecrease of the capacity of the other.

' The load-deflection characteristics of the said embodiment (Figure '7)may also be made to follow optimum values by changing the hydraulicaction during deflection by varying the sizes of the orifices throughwhich the hydraulic medium must flow between the two chambers 6 l, 63.This may be done by designing the mount so that during greaterdeflections, the lower end 53 of the inner spring element 49, spanningthe channels 45, will sag somewhat into said channels so as to restrictthe orifices therethrough and thereby slow down the flow of the medium.

The mounting shown in Figure 7 also operates to absorb vibrations andshocks in a horizontal direction. Horizontal deflections of the baseplate 4| result in putting both the spring elements 49, 5| into shear.Here, as in vertical movements, the deflections are curtailed withoutthe use of abruptly acting snubbers, by means of spring and hydraulicactions, much as described above in connection with the firstembodiment.

To appreciate the superiority of mounts embodying the present invention,some study of load-deflection curves is profitable. Many commercialmounts today have a substantially linear load-deflection curve; that is,deflection and load increase at about a constant ratio except that,toward the end of the curve, the load increases more rapidlythan thedeflection. Thus. a 19%!- deflection curve for such a mountis a fairlystraight slanting line which swings upward steeply toward the end.

Mounts embodying the present invention, on the other hand, as alreadyexplained, are relatively stiii at first, then get softer, and finallyget stiff again. Thus, a load-deflection curve for such mounts isinitially quite steep and then proceeds at a lesser slope and finallyswings upward again to the end of the curve.

It should be understood that a shock mount which has the bestload-deflection curve is one which, for a given displacement and energyabsorption, will transmit the smallest forces.

One of the members to which a shock mount is fastened, such as thechassis of a motor vehicle in the examples mentioned above, has acertain kinetic energy due to its movement. This energy must be acceptedideally by the shock mount. The energy is translated in the shock mountto the potential energy involved in straining the resilient material.The potential or strain energy is the work done in deforming the mountand it is-equal to the area under the portion of the load-deflectioncurve traversed. The greater the thrust to which a mount is subjectedand, hence, the greater the attendant kinetic energy, the larger thearea under the curve.

Thus, it is seen that a mount is most satisfactory when its deflectioncurve is such that, for a given deflection, the area under the curve isat a maximum. It is obvious that a load-deflection curve, which isinitially steep and then proceeds at a lesser slope (as in the presentmount), will provide more area under it and, hence, more energyabsorption than a deflection curve which is relatively linear (as istypical of present commercial shock mount practice, as mentioned above).

For thrusts having relatively large energy, it will be understood that,to absorb said energy, a relatively large area under the load-deflectioncurve is necessary. As the load-deflection curve of the present mountprovides such area throughout the beginning of the curve, the deflectionof the mount need not be as great as for commercial mounts having arelatively linear curve and, hence, the force transmitted by the presentmount is less than that transmitted by such commercial mounts.

Although the embodiments shown in the drawings have particulargeometries, it will be understood that various changes in geometry maybe made within the spirit of the invention. Such changes in geometry andrelative sizes of elements, and other modifications, may be made to suitthe present mounting to different compounds of natural or syntheticrubber, to dinerent hydraulic mediums and to different loading values.

Although not shown in the illustrated embodiments, it would be advisableto incorporate means for injecting the hydraulic medium into thechambers 35U, 35L, 3'! (of Figure 1-6) and the chambers Si, 63 (ofFigure 7) after the mountings are assembled.

It will be understood that each of the mounts described will alsooperate with its base plate secured to a load and its load spool or loadplate secured to a base.

While there have been described what at present are considered threepreferred embodiments of the present invention, it will be obvious'tothose skilled in the art that various changes-andmodifications may bemade therein without de- 13 parting from the invention and it is,therefore, aimed in the appended claim to cover such changes and.modifications as fall within the true spirit and scope of the invention.

What is claimed is:

A mounting to sustain a load relative to a base, comprising a loadspool, including two mutually parallel spaced end plates, and a corerigidly joining said end plates and normal thereto; a substantiallytire-shaped spring collar encircling said core, intermediate said loadplates, and longitudinally slidable upon said core; substantiallyradially disposed spring fingers defining slots through the wall of saidspring collar, said spring fingers undergoing compression under slightthrusts in a radial direction and collapsing into flexure under greaterthrusts in a radial direction; a base plate pierced by a central openingsecured to the outer periphery of the spring collar, said base platebeing disposed intermediate the load plates and substantially parallelthereto; two tubular spring elements disposed coaxially with the coreand spaced therefrom, said spring elements being interposed between theload plates and on opposite sides of the base plate, each being securedat one end to one of the load plates and at the other end to the baseplate; the base plate being pierced by fixed restricted orificespositioned between the spring collar and the spring elements; eachspring element compressing as a column under slight axial thrusts andcollapsing into inward flexure under greater axial thrusts; twohydraulic chambers of substantially annular configuration disposedrespectively on opposite sides of the base plate and at least partiallybounded by the two tubular spring elements; said hydraulic chambersintercommunicating through the fixed oriflees in the base plate and theslots through the spring collar; a hydraulic medium within saidchambers; the spring collar, upon axial deflections of relatively largeamplitude, pressing against one or the other of the load plates andthereby reducing the flow of the hydraulic medium through said slots.

NORMAN E. LEE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,080,919 Ihln May 18, 1937 2,351,427 Henshaw June 13, 19442,380,899 Strachovsky July 31, 1945 2,379,763 Sweet July 3, 19452,382,372 Wallerstein Aug. 14, 1945 2,535,080 Lee Dec. 26, 19502,539,443 Lee Jan. 30, 1951 FOREIGN PATENTS Number Country Date 50,1France Oct. 10, 1939 OTHER REFERENCES Crede: Vibration and ShockIsolation, 1951. (Copy in Div. 52.)

